The present invention relates to a method for identifying damage in toothed transmission stages having at least one pair of meshing toothed wheels and to an apparatus for identifying damage on toothed transmission stages.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Transmissions are central components in a large number of industrial machines. During operation they are subject to a high level of stress and associated wear, leading to the possibility of damage occurring, which might result in impaired operation and in particular failure of the transmission and the machine as a whole. To minimize or prevent such failure due to damage and the associated financial losses, it is desirable to observe the operation of the transmission. In this context condition monitoring system CMS are used during ongoing operation to monitor whether a component, for example a transmission, operates in the required manner or whether there is a malfunction present or developing. The occurrence or imminence of damage can thus be identified early, so that suitable measures can be instituted to limit the damage locally or to eliminate it in a timely and efficient manner. It is thus possible to keep operating restrictions and stoppages of the machine to a minimum by identifying damage at an early stage.
At present, such condition monitoring systems are becoming increasingly important in the context of wind power energy generation, as the constant reliable operation of the wind power plant has to be ensured for a continuous power supply and is essential for economical operation of the system. Particular attention is paid here to monitoring the condition of the transmission, as the transmission of the wind power plant has the longest down times per damage incident of all the components of the wind power plants. The long downtime here is due to complex repair procedures and sometimes poor accessibility of the damaged components.
A condition monitoring or condition diagnosis system, as used in the field of wind power, generally includes monitoring the temperature of the system, monitoring the condition of the oil used in the system and oscillation monitoring. In the latter instance the oscillations associated with the operation of a component are monitored by means of suitable vibration transducers in order to be able thus to detect deviations from the normal operation of the wind power plant or its components, indicating the presence of damage. Current operating parameters such as speed or load are also monitored and recorded.
With the known methods condition monitoring generally takes place over quite a long period. To identify damage, the detected signals are compared with reference values, which were detected during a calibration measurement or obtained with the aid of simulation methods. Oscillation signatures can be cataloged, which were detected in the presence of damage and are then available for comparison with oscillation signatures that are detected in the future. However a reliable damage prognosis by comparison can only take place, if identical operating parameters prevailed during the detection of the cataloged oscillation signatures and the oscillation signatures with which these are compared.
However, highly variable wind speeds mean that a wind power plant is subject to a broad load spectrum and the operational parameters extend over a wide range. It is therefore generally not possible, or it is only possible with a high level of outlay, to store reference values for all possible operating states of the system. For this reason what is known as an envelope curve technique is used. This means that a minimum value and a maximum value are assigned in each instance to the reference signal, allowing the range of operational deviations to be estimated and defined. A deviation is then interpreted as being due to damage if the signal lies outside this reference window. However this is associated with inaccuracies and for reliable damage identification it is necessary to draw on the services of an expert who analyzes the detected signals and uses his/her experience to identify possible damage. This is considered disadvantageous, as the plurality of installed wind power plants in particular means that there are not enough experts available and their deployment for identifying damage is associated with high costs.
Efforts are therefore being made to improve the analysis of the data acquired as part of condition monitoring in respect of damage present. It is therefore necessary in particular for a reliable damage prognosis to separate the changes in the detected signals caused by a change in current operating parameters from the changes due to damage.
It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved method for damage identification, which allows reliable identification and prediction of damage on transmissions, so that damage can be identified automatically and economically.